Project Summary Diabetic stroke patients have higher mortality and worse neurological outcomes. Emerging clinical and experimental data suggest that BBB disruption, neuroinflammation, and stroke recovery impairment are exacerbated in T2D. Hence, the goal of this project is to investigate therapeutic approaches that can target these specific T2D mechanisms in stroke. Fibroblast Growth Factor-21 (FGF21) is a circulating endocrine hormone that is primarily expressed in the liver. FGF21 has pleiotropic metabolic actions, but also has tissue protective and repair roles. Here, we will test the overall hypothesis that exogenous recombinant human FGF21 (rFGF21) activates FGFR1-?-klotho complex that may ameliorate T2D-affected mechanisms after stroke via: (1) activation of PPAR? for BBB protection, (2) inhibition of NF?B-mediated but activation of PPAR? for neuroinflammation modulation, (3) promotion of AMPK/Nrf2-mediated vascular/white matter remodeling to boost neurorestoration after stroke. Aim 1. Investigate rFGF21 effects on blood-brain barrier integrity in T2D stroke mice. We will examine FGF21 specific receptor FGFR1 phosphorylation, PPAR? activity, BBB integrity, hemorrhagic transformation, expression of vascular inflammatory molecules and tight junction proteins, are assessed up to 3 days after stroke (dMCAO) in db/db T2D mice, and T2D stroke in vitro model of brain endothelial/astrocytes co-cultures. Aim 2. Investigate rFGF21 effects on neuroinflammation in T2D stroke. We will examine NF?B and PPAR? activation, and correlation with microglia/macrophage activation, pro-inflammatory factor expression in peri- lesion area by RT-PCR, immunohistochemistry, western blots, and flow cytometry after focal dMCAO stroke in T2D mice, and in primary microglia cultures in vitro. Aim 3. Investigate rFGF21 effects on vascular/white matter remodeling in T2D stroke. We will examine activation of AMPK and Nrf2, expression of trophic factors in isolated brain microvascular fragments and brain tissues by western blot analysis, immunohistochemistry, and mRNA microarray. We will also test biomarkers of vascular and white matter remodeling over time by immunohistochemistry, RT-PCR and western blots after ischemic stroke of T2D mice, and in vitro models of primary human brain endothelial cultures and oligodendrocyte cultures.